what are the Data Flow Diagrams DFD?

Question

What are DF Diagrams , and how they help project managers in their job?

Answer 1

As you can see, is a data flow diagram a diagram that shows the dataflow in an application.

At the highest level you have the context diagram that can be represented as:

          +-------------+
input --> | Application | --> output
          +-------------+

You can zoom into the function to show detailed dataflow:

          +-------+      +--------+     +----------+
code  --> | lexer | -->  | parser | --> | treetool | --> grapical representation
          +-------+      +--------+     +----------+
              |              ^                 ^
              |              |                 |
              |              V                 |
              |    ================            |
              +--> | symbol table | -----------+
                   ================

As you see, there are functions and data stores. Functions can change the data and datastores are used to store and retrieve the data.

Answer 2

Data Flow Diagram (DFD) is graphical representation of flow of data/info. It is used to show how data is moved between different processes.

There are 4 basic notation elements:

• Circle: Operation
• Box: Sink of information, (input/output)
• Parrallel Bar: Data store / File / Database
• Arc: Flow of info/data

DFS's are in problem domain rather than in solution domain. They are basicly top level model of how something operates based on flow of information. Also there is no support for concurrency representation in DFD.

Following is an example:

Answer 3

The "What" is explained above.

DFD's don't help project managers. DFD's are mainly useful for developers to get a good overview of how data flows between components in a (sub)system.